1. Field of the Invention
This invention is directed to a speaker box, more particularly to a speaker box for a radio or the like that is suitable for mounting in an automobile.
2. Description of the Prior Art
It has become common practice to make speaker boxes and/or speaker covers for car radios of plastic as can be seen from, for example, published examined Japanese patent application No. 57(1982)-9274.
The conventional plastic speaker boxes are generally formed by injection molding and thus have to be molded in at least two separate parts. The separately formed parts are then fastened together by screws, bonding, welding or the like.
When assembling a speaker box by one of these methods, however, it is necessary to ensure snug and precision fitting of the joint faces with one another. This need arises because if the speaker box should allow any leakage of air, noise will be produced when air pressurized by the movement of the speaker cone escapes from the speaker box. In severe cases, there may even be an adverse effect on acoustic performance such as, for example, a lowering of the sound pressure in the low frequency range. When the speaker box components are assembled using screws, for example, it is necessary to use a packing material between the joined edges, or to use components made of thick material so as to ensure proper sealing by virtue of the plastic deformation of the component material, or to space the screws at close intervals. However the assembly is accomplished, the conventional method of forming speaker boxes by injection molding turns out to involve a relatively large number of complicated fabrication steps and to result in relatively high production cost. Moreover, with the conventional method, no matter how much care is used to ensure proper sealing among the components during assembly, there will always remain some possibility of air leakage. On the other hand, it is not easy to detect faulty sealing prior to product shipment.